TIME DILATION: an experiment with mu-mesons This classic film documents an experiment done in 1963 the results of which can only be explained when one accepts the consequence that moving clocks run slow. This phenomenon is known as time dilation. The timekeeping device is the mu-meson, a subatomic particle with origins away from the Earth moving at relativistic speed. What follows here is an explanation of the experiment described in that film. Many mu-mesons rain down every hour on the...